The Cliff House Sandstone is a transgressive sequence of marine sandstones which overlies the Menefee Formation. The three principle Cliff House units (Lower, Intermediate, and Upper) visible in Chaco Canyon represent the beach, near shore marine, and offshore marine deposits produced near a barrier island beach front by repeated incursions of the Western Interior Seaway.
The Lower Sandstone unit, a massive marine sandstone, forms the 80 - 100 foot prominent cliffs visible throughout the canyon. This sandstone was deposited just off of a Late Cretaceous beach, in relatively shallow water still affected by wave and storm action. An abundance of ripple marks are visible in this unit. Fossils include shells and casts from clams, ammonites (including possible Placenticeras) snails, and shark's teeth. Iron-cemented, knobby casts of burrows known as Ophiomorpha ("serpent shape") Nodosa ("nodular") are particularly abundant. These casts are thought to be the fossilized remains of burrows left by a small shrimp-like crustacean known as Callianasa.